Novel process for trimerizing polyisocyanates

ABSTRACT

A novel catalyst combination for the trimerization of polyisocyanates to polyisocyanurates is disclosed. The catalyst combination comprises (i) a tertiary amine trimerization catalyst, (ii) an alkali metal salt of an N-substituted amide, and (iii) a dibutyl tin di(alkanoate) compound. The use of this catalyst combination in the preparation of polyisocyanurate spray foams enables the systems to be sprayed in either a 1:1 or 2:1 by volume ratio, or ratios between these limits interchangably with no alterations being required in reactant formulations. The polyisocyanurate foams produced using the novel catalyst combination of the invention are characterized by having high resistance to flame and heat distortion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of our copending application Ser. No.437,781 filed Jan. 30, 1974 now U.S. Pat. No. 3,899,443.

BACKGROUND OF THE INVENTION

1. Field of the Invention polyisocyanates to polyisocyanurates and

This invention relates to the preparation of polymer foams and is moreparticularly concerned with novel catalyst combinations for thetrimerization of polyisocyanurates ad their utilization in thepreparation of polyisocyanurate foams.

2. Description of the Prior Art

Rigid polyisocyanurate foams having high resistance to flame and heat aswell as excellent thermal insulating capacity are known in the art. Theprior art discloses methods for preparing such foams by reacting anorganic polyisocyanate with a trimerizing catalyst in the presence of ablowing agent, and a minor proportion (usually less than 0.5 equivalentper equivalent of polyisocyanate) of a polyol; see for example U.S. Pat.Nos. 3,516,950, 3,580,868, 3,620,986, 3,625,872, and 3,725,319. Theprocess described in U.S. Pat. No. 3,745,133 discloses the use of acombination of an epoxide and a tertiary amine as cocatalysts.

The above methods require the foaming process to proceed in conjunctionwith at least two polymer forming reactions; namely, the isocyanurateformation arising from the homopolymerization of the isocyanateemployed, and the minor amount of polyurethane formation arising fromthe reaction of a polyol with the isocyanate. Difficulties arise,particularly in commercial applications, due to the variation inrelative rates of the two polymerization reactions. The polyurethaneformation frequently initiates before the trimerization formation thusgiving two separate rise steps in the overall foam rise profile.

These difficulties are accentuated in the case of application ofpolyisocyanurate foams by spray techniques. The latter normally requirethat the polyisocyanurate foam forming mixture be supplied in only twostreams to the mixing and spraying head. Further these two streams arenormally so formulated, by appropriate preblending of components, thatthey can be brought together either in equal ratio by volume or with thepolyisocyanate containing component in twice the ratio by volume of theother component. These requirements are largely dictated by the designof spray equipment currently available.

It would obviously be highly desirable to use the same two componentsfor either of the above ratios or any ratios intermediate therebetween.However, because of the critical role which the nature and proportion ofcatalyst plays in the preparation of polyisocyanurate foams, it has nothitherto been possible to devise a catalyst which would performsatisfactorily at the different catalyst levels which result when thecomponent ratios are changed in the above manner. Accordingly it hashitherto been necessary to provide substantially different formulationsfor operation at the different component ratios. Further it has evenbeen very difficult to formulate a system which could be operatedsatisfactorily when the two components of the system are employed inequal ratio by volume.

We have now found a catalyst system which is free from the abovedifficulties and which is particularly useful in spray foam systems.

SUMMARY OF THE INVENTION

This invention comprises a cocatalyst system for the trimerization of apolyisocyanate which cocatalyst system comprises:

a. from about 10 to about 70 mole percent of a teritary aminetrimerization catalyst;

b. from about 20 to about 80 mole percent of an amide salt having theformula ##STR1## wherein M is an alkali metal, R₁, R₂, R₃ can be thesame or different and are selected from the group consisting of H,lower-alkyl, aryl, aralkyl, and cycloalkyl, R₄ is selected from thegroup consisting of lower-alkyl and aryl; and

c. from about 3 to about 30 mole percent of a dibutyl tin di(alkanoate)wherein the alkanoate residue contains from 2 to 12 carbon atoms,inclusive.

The invention also comprises an improved process for the preparation offlame and heat resistant cellular polymers, particularly in the form ofspray foam in which the major recurring polymer unit is isocyanuratewhich process comprises bringing together, in the presence of a blowingagent, a polyisocyanate, a minor amount of a polyol, and a cocatalystsystem as recited hereinabove.

The invention also comprises the cellular polymers produced inaccordance with the above process.

The term "lower alkyl", means alkyl compounds having from 1 to 8 carbonatoms, inclusive, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, and isomeric forms thereof. The term "aryl" means phenyl,tolyl, xylyl, napththyl, diphenylyl and the like. The term "aralkyl"means benzyl, p-methylbenzyl, p-ethylbenzyl, β-phenylethyl,naphthylmethyl, and the like. The term "cycloalkyl" means cyclobutyl,cyclopentyl, cyclohexyl, methyl-cyclohexyl, cyclooctyl, and the like.The term "alkali metal" means sodium, potassium, and lithium.

In the dibutyl tin di(alkanoate) the term, "alkanoate residue containsfrom 2 to 12 carbon atoms, inclusive", includes, acetate, propionate,butyrate, valerate, caproate, enanthoate, capryloate, pelargonate,capriate, hendecanoate, laurate and isomeric forms thereof.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, the need to balance two different reactions, namelythat leading to urethane and that leading to isocyanurate, in thepreparation of polyisocyanurates makes the choice of catalystparticularly important. This is especially so in the preparation ofsystems for application by spray techniques.

It is an object of the present invention to prepare high temperature andfire resistant polyisocyanurate cellular polymers, particularly by sprayapplication on a variety of substrate materials. It is a further objectto provide formulations which can be employed for spray at ratios from1:1 to 2:1 or ratios therebetween, and can be changed from one ratio toanother without the need for changing formulations or catalystconcentration in any way.

It is well known to those skilled in the spray foam art that two streamsof reactants feed into a spray gun. The A component contains thepolyisocyanate being used along with any other additives non-reactivewith the isocyanate, such as blowing agent, etc. In the polyurethanespray art, the B component contains the polyol component in equivalentamount to the polyisocyanate along with the catalyst, surfactant, orother additives non-reactive with the polyol, or catalyst. For obviousmechanical reasons it is advantageous to formulate the components sothat A and B can be pumped at a 1:1 volume ratio. In normal practice,the ratio of A:B will not be exactly 1:1 on a weight basis. However, inspraying polyisocyanurate foams wherein the polyol component is presentonly in minor amounts, it is necessary to make extensive formulationadjustments in order to obtain a 1:1 by volume ratio. Usually, thedeficiency in the B volume side is made up by the addition of otheradditive materials such as non-reactive fire retardants and the like.The catalyst concentration required to provide optimum risecharacteristics for that particular formulation is determined andbecomes a constant thereto. When spraying a polyisocyanurate foam at a2:1 volume ratio, the optimum catalyst concentration applicable theretowill be different from that at the 1:1 ratio, assuming the same catalysthas been employed.

We have now found, surprisingly and unexpectedly, that a particularcocatalyst combination set forth herein permits the formulation of aspray system which can be used as 1:1 or 2:1 ratio spray without need tomake any adjustment to reactant or catalyst proportions in order toobtain satisfactory spray foam. The advantages which flow from suchfinding will be readily apparent.

The novel catalyst combinations of the present invention comprise theingredients set forth above.

The cocatalyst components are brought together during or immediatelyprior to the trimerization reaction of the polyisocyanate. In anoptional step the tertiary amine and amide salt (I) can be premixed orstored as a mixture in which case the dibutyl tin di(alkanoate) is keptseparate until it is desired to carry out the trimerization process ofthe invention.

The components of the catalyst combination of the invention and theconcentration ranges of said components are set forth hereinbelow indetail in the form of mole percentages. It is to be understood that thesum total of the individual mole percent concentrations chosen for eachcomponent must equal 100 mole percent. It is also to be understood thatconcentrations of one or more components can be varied within thespecified ranges so long as the appropriate adjustments are made in oneor more of the remaining components so that the total mole percent is100. This method of indicating the proportions of the three componentsof the cocatalyst is adopted in defining the parameters of thecocatalyst itself. However, when particular embodiments of the use ofthe cocatalyst are described hereinbelow, e.g. in the preparation of apolyisocyanurate cellular polymer, the amounts of the components of thecocatalyst will be set forth in absolute terms.

1. The teritary amine component of the cocatalyst combination isadvantageously employed in the combination in a proportion in the rangeof from about 10 mole precent to about 95 mole percent and, preferablyfrom about 10 mole percent to about 70 mole percent. The said tertiaryamine component can be any of the tertiary amine trimerization catalystsknown in the art and includes those amines set forth in U.S. 3,745,133in Column 8, lines 1-73 and which are herein incorporated by reference.A particularly preferred class of tertiary amines consists of thefollowing: N,N-dimethylethanolamine, N,N-dimethylcyclohexylamine,N,N-dimethylbenzylamine, N,N,N',N'-tetramethyl-1,3-butanediamine,N,N,N',N'-tetramethylpropanediamine, N-methylmorpholine,N-ethylmorpholine, andN,N',N"-tris(dimethylaminopropyl)hexahydrotriazine. A particularlypreferred species of teritary amine is N,N-dimethylcyclohexylamine.

2. The amide salt component of the cocatalyst combination having theformula (I), is advantageously employed in a proportion in the range offrom about 2 mole percent to about 85 mole percent of the cocatalystand, preferably, in the range from about 20 mole percent to about 80mole percent. The compounds of formula (I) are prepared by bringingtogether under anhydrous conditions the appropriate acid salt of formula##STR2## dissolved in a solvent, with the appropriate organic isocyanateof formula R₄ NCO wherein R₁, R₂, R₃, R₄, and M have the significancedefined above. The isocyanate is added slowly to the salt solutionwhereupon an exotherm occurs and carbon dioxide is evolved.

Examples of solvents for the above reaction include low molecular weightpolyols such as ethylene glycol, diethylene glycol, dipropylene glycol,dibutylene glycol, tetraethylene glycol, glycerol, the liquidpolyethylene glycols such as the polyoxyethylene glycols prepared by theaddition of ethylene oxide to water, ethylene glycol or diethyleneglycol, and the like; Cellosolve, butyl Cellosolve, Carbitol, methylCarbitol, butyl Carbitol, and the like; ethanolamine, diethanolamine,triethanolamine; and dipolar aprotic solvents such as dimethylformamide, dimethyl acetamide, N-methylpyrrolidone, dimethyl sulfoxide,and the like; and mixtures of any of the aforesaid solvents. Thereaction between the acid salt and the isocyanate compound is so muchfaster than the reaction between the isocyanate compound and thehydroxyl containing solvents, that the rate difference allows the use ofthe latter as a preferred class of solvents. The preparation of thecompounds of formula (I) is illustrated by the following equation:##STR3## In an optional step the solvent can be removed, however, it isusually found advantageous to leave the salt dissolved in the solventand thereafter use the catalyst in combination with its diluent. Whenthe solvent is removed, the amide salt can be used in its isolated form;however, precautions should be taken to protect it from atmosphericmoisture prior to its use in the cocatalyst combination.

Typical examples of the starting acid salt include: sodium acetate,potassium acetate, lithium acetate, sodium propionate, potassiumpropionate, lithium propionate, sodium hexanoate, potassium hexanoate,lithium hexanoate, potassium decanoate, potassium 2-methylhexanoate,potassium 2-ethylhexanoate, potassium neopentanoate, sodium phenylacetate, poatassium phenyl acetate, lithium phenyl acetate, potassiumβ-phenyl propionate, potassium p-tolyl acetate, potassium cyclohexylacetate, potassium 4-methylcyclohexyl acetate, potassium β-cyclohexylpropionate, and the like. Typical examples of the starting organicisocyanate include: butyl isocyanate, octyl isocyanate, phenylisocyanate, tolyl isocyanate, and the like. The proportions of reactantsemployed in preparing the compound (I) are in the molar ratio of 1:1.

A particularly preferred species of amide salt having the formula (I) ispotassium N-phenyl-2-ethylhexamide.

In a preferred embodiment of the invention the salt (I) is employed inthe cocatalyst in combination with a diluent. The diluent can be thereaction solvent, or mixtures thereof, employed in the preparation ofcompound (I). A particularly preferred class of diluents consists ofethylene glycol, diethylene glycol, polyethylene glycol 400, andmixtures thereof and mixtures of this preferred class with dimethylformamide. A particularly preferred diluent mixture consists of ethyleneglycol and dimethyl formamide. The concentration of the salt (I)dissolved in the diluent is not critical and can vary from about 25percent to about 75 percent by weight. When a mixture of diluents isused the proportion by weight of one diluent in the other isadvantageously from about 10 to about 90 percent by weight, andpreferably from about 25 to about 75 percent by weight.

3. The tin salt component of the cocatalyst system, is advantageouslyemployed in a proportion in the range of from about 1 mole percent toabout 45 mole percent and, preferably from about 3 mole percent to about30 mole percent. The tin salt component can be any of the dibutyl tindi(alkanoate) compounds known in the foam art as urethane type catalysts(see M & T Chemicals, Inc., Bulletin C-66) and includes dibutyl tindiacetate, dibutyl tin dioctoate, dibutyl tin di-2-ethyl-hexoate, anddibutyl tin dilaurate. A particularly preferred tin salt compound of thecocatalyst combination is dibutyl tin diacetate.

While the catalyst combination described hereinabove specificallyrequires the use of three different catalyst components in combination,it is to be understood that this does not exclude the presence in thecatalyst combination of additional components or agents capable ofcausing the trimerization of a polyisocyanate provided the threecomponents discussed above are present.

The polyols employed in preparing polyisocyanurate foams in accordancewith the present invention can include any of the polyols set forth inU.S. Pat. No. 3,745,133, incorporated herein by reference, or any ofthose known in the art to be useful as a minor component in thepreparation of polyisocyanurate foams; see supra. Said polyols can beadded separately during the trimerization of the polyisocyanatecomponent, or can be prereacted with the polyisocyanate to form anisocyanate terminated prepolymer which is subsequently trimerized. Thepolyols are advantageously employed in the range from about 0.01equivalent to about 0.3 equivalent per equivalent of isocyanate.

The polyisocyanates employed in the preparation of polyisocyanuratefoams in accordance with the present invention can be any of the organicpolyisocyanates conventionally employed in the art for this purposepreviously; see the art cited supra. Advantageously, in order to obtainfoams having exceptionally high heat resistance and structural strength,the polyisocyanates employed in the process of the invention arepolymethylene polyphenyl polyisocyanates, particularly those set forthin U.S. Pat. No. 3,745,133. A particularly preferred form ofpolymethylene polyphenyl polyisocyanate is one having an acidity,expressed as "% hot HCl" of less than about 0.1 percent. Various methodsof reducing the acidity to such levels are known in the art. Aparticularly useful process is that set forth in German OLS No.2,249,375. The latter process comprises treating the polyisocyanate withfrom 0.25 to 1 equivalent of monomeric epoxide for each equivalent ofacid present in the polyisocyanate.

In carrying out the preparation of polyisocyanurate foams in accordancewith the process of the invention, the procedures and equipmentconventional in the art are employed. The proportions of cocatalyst areso chosen that, for each equivalent of polyisocyanate present in thereaction mixture, there is employed from 0.005 to 0.04 equivalent,preferably from 0.01 to 0.03 equivalent, of said tertiary aminecomponent, from 0.001 to 0.03 equivalent, preferably from 0.003 to 0.02equivalent of said compound (I), and from 0.0005 to 0.005 equivalent,preferably from 0.001 to 0.003 equivalent of said compound (II).

Foaming agents, and other optional additives such as dispersing agents,cell stabilizers, surfactants, flame retardants, and the like, can beemployed according to the teachings of the incorporated reference. Aparticularly preferred class of flame retardant additives are thephosphorus containing flame retardants, such as:tris(2-chloroethyl)phosphate, tris(2-chloropropyl)-phosphate,tris(2,3-dibromopropyl)phosphate, tris(1,3-dichloroisopropyl)phosphate,and the like.

As set forth above, the use of the cocatalyst combination of the presentinvention provides for the spray application of polyisocyanurate heatand flame resistant foams at variable spray ratios of 1:1 to 2:1 andratios therebetween without the need for changing foam formulations.Standard foam spraying equipment well known to those skilled in the artcan be used in carrying out the specific embodiments of the presentinvention. This includes the various types of spray guns known to thoseskilled in the art. The foams made in accordance with the invention showgood adhesion to a variety of substrates including masonite, buildingboard, gypsum board, asbestos board (transite), wood, plywood, sheetmetal, and paper products such as Kraft paper and heavy cardboard. Thus,the cellular products of the invention can be employed for all thepurposes for which the currently produced cellular spray products areconventionally employed and are particularly suitable for applicationswhere thermal resistance, low flame spread and low smoke generation oncombustion are required.

For example, the cellular products of the invention can be employed asthermal barriers and insulating materials when sprayed on hightemperature pipe lines, ovens, and storage tanks containing fluids atelevated temperatures. The foams made in accordance with the presentinvention also find use in cryogenic applications where insulation ofpipes or tanks holding fluids at low temperatures require thermalinsulation.

The particular embodiment of the variable spray ratio provides for aunique advancement in the spray foam art whereby an object requiringinsulative protection, for example, a storage tank containing a liquidat an elevated temperature, is sprayed with the polyisocyanurate foam ofthe invention at the 1:1 component ratio. This provides a covering ofcellular foam having the optimum insulation value. Then the pumpingratio is changed to 2:1 and a second layer of higher density cellularfoam is applied over the first, thereby affording protection for thefirst layer by virtue of its higher physical strength. This embodimentof the invention obviates the necessity of varying formulations when itbecomes necessary to change the density of the foam being sprayed, whichfinds special utility when spraying foam in remote areas. The heat andflame resistant foams of the present invention are particularly usefulbecause of their ease of application in the construction of industrialbuildings.

Non-cellular polymers can also be made in accordance with the presentinvention using standard techniques known to those skilled in the artbut employing the cocatalyst combinations of this invention. Solidpolymers are obtained by carrying out the trimerization of apolyisocyanate using the same reactants employed in the cellularpolymers but in the absence of the blowing agent. The reactants can becast, molded, coated, or otherwise deposited by methods known to thoseskilled in the art, to form a solid polyisocyanurate casting, molding,coating, or other form of solid polyisocyanurate. Such products find usefor example, in high temperature resistant laminates prepared fromreinforcing layers of heat resistant fabric such as glass fabric,graphite fabric, and the like, and layers of polyisocyanurate of theinvention.

The following preparations and examples describe the manner and processof making and using the invention and set forth the best modecontemplated by the inventors of carrying out the invention but are notto be construed as limiting. The pertinent test procedures relating tothe invention are defined as follows.

Acidity Determination

Two grams of the isocyanate to be analyzed is mixed with 75 ml. each oftoluene and methanol in a 250 ml. Griffin beaker. The beaker is coveredwith a watch glass and the mixture refluxed for 5 minutes with stirring.The mixture is then allowed to cool to room temperature. Employing aFisher Accumet pH meter with combination electrode, the mixture istitrated at a constant rate with 0.02 N potassium hydroxide in methanolto a pH of 7.7. A standard blank is prepared by carrying a mixture of 75ml. each of toluene and methanol through the same procedure outlinedabove. The acid content of the isocyanate is then calculated accordingto the equation:

    % Acid = (A - B) × 0.0365

wherein A is the number of milliters of potassium hydroxide solutionused to titrate the isocyanate mixture and B is the number of millitersof potassium hydroxide used to titrate the standard blank.

The number of equivalents of acid present in a given polyisocyanate aredetermined by the formula: ##EQU1##

Preparation 1 Potassium N-phenyl-2-ethylhexamide ##STR4##

A 1 liter 3 neck flask was fitted with a mechanical stirrer, athermometer, an addition funnel, and a gas in-let tube. The apparatuswas thoroughly dried and then the flask was charged with 182.2 g. (1.0mole) of potassium 2-ethylhexanoate dissolved in 168 g. of ethyleneglycol. During constant stirring and under a slight nitrogen pressure,119.1 g. (1.0 mole) of phenyl isocyanate was slowly added dropwise. Thereaction mixture exothermed to 60° C and carbon dioxide was evolved. Theresulting clear solution started to precipitate small crystals uponcooling. However, the addition of 175 g. of dimethyl formamide yielded aclear yellow solution having the following properties: Equivalent weight= 141; Acid No. = 3.4; Viscosity at 25° C = 53 cstk. This solution ofpotassium N-phenyl-2-ethylhexamide can be used directly as a catalystcomponent. A crude yield of the salt was obtained when ethylene glycoland dimethyl formamide were removed by heating the solution at steambathtemperature under 0.2 mm. pressure and protecting the product fromatmospheric moisture. A semi-crystalline orange residue remained, wt. =275 g. It was stored in a vacuum desiccator until used as a cocatalystcomponent.

Preparation 2 Potassium N-butyl-2-ethylhexamide ##STR5##

A 1 liter 3 neck flask equipped as in Preparation 1 was charged with182.2 g. (1.0 mole) of potassium 2-ethylhexanoate dissolved in 158 g. ofethylene glycol. During constant stirring 99.1 g. (1.0 mole) of butylisocyanate was slowly added dropwise. The reaction mixture evolvedcarbon dioxide and exothermed to about 50° C. The resulting clear yellowsolution showed an increase in viscosity over the starting solution andhad the following properties: Equivalent Weight = 90; Acid No. = 3.8;Viscosity at 25° C = 560 cstk. This solution of potassiumN-butyl-2-ethylhexamide can be used directly as a catalyst component. Acrude yield of the salt was obtained when the ethylene glycol wasremoved by heating the solution at steam-bath temperature under 0.2 mm.pressure and protecting the product from moisture. A semi-crystallineorange residue remained, wt. = 267 g. It was stored in a vacuumdesiccator until used as a cocatalyst component.

Preparations 3-14

Using the procedure of Preparation 1 wherein 168 g. of ethylene glycoland 175 g. of dimethylformamide were used together as co-solvents andsubstituting the alkali metal carboxylic acid salts and organicisocyanates set forth in the following table, the corresponding amidesalts were obtained as listed therein. The salts are characterized bythe percent by weight of solvent content which itself consisted of 49percent by weight of ethylene glycol and 51 percent by weight ofdimethyl formamide. Removal of the solvent to provide the crude yield ofamide salt was readily accomplished by heating the solution in vacuo.

    __________________________________________________________________________        Acid Salt  Isocyanate                 Solvent %                           Prep.                                                                             (1.0 mole) (1.0 mole)                                                                             Product           (by wt.)                            __________________________________________________________________________    3   Na.sup.1 acetate                                                                         Phenyl-  Na N-Phenylacetamide                                                                            68                                  4   K.sup.2 acetate                                                                          Phenyl-  K N-Phenylacetamide                                                                             66                                  5   Li.sup.3 acetate                                                                         Phenyl-  Li N-Phenylacetamide                                                                            70                                  6   K propionate                                                                             Phenyl-  K N-Phenylpropionamide                                                                          65                                  7   Na 2-ethylhexanoate                                                                      Phenyl-  Na N-Phenyl-2-ethylhexamide                                                                     59                                  8   K 2-ethylhexanoate                                                                       p-Tolyl- K N-(p-Tolyl)-2-ethylhexamide                                                                   55                                  9   Li 2-ethylhexanoate                                                                      α-Naphthyl-                                                                      Li N-(α-Naphthyl)-2-ethylhexamide                                                         55                                  10  K decanoate                                                                              4-Biphenylyl-                                                                          K N-(4-Biphenylyl)-decanoamide                                                                  49                                  11  K β-phenylpropionate                                                                Phenyl-  K N-Phenyl-β-phenylpropionamide                                                            57                                  12  K cyclohexylacetate                                                                      Phenyl-  K N-Phenyl-cyclohexylacetamide                                                                  57                                  13  K phenylacetate                                                                          Phenyl-  K N-phenylacetamide                                                                             58                                  14  K α-naphthylacetate                                                                Phenyl-  K N-Phenyl-α-naphthylacetamide                                                            53                                  __________________________________________________________________________     .sup.1 Na: Sodium                                                             .sup.2 K : Potassium                                                          .sup.3 Li: Lithium                                                       

Preparations 15-22

Using the procedure of Preparation 2 wherein 158 g. of ethylene glycolwas used as solvent, and substituting the potassium carboxylic acidsalts and organic isocyanates set forth in the following table, thecorresponding amide salts were obtained as listed therein. The salts arecharacterized by the percent by weight of solvent content of ethyleneglycol. Removal of the solvent to provide the crude yield of amide saltwas readily accomplished by heating the solution in vacuo.

    __________________________________________________________________________        Acid Salt  Isocyanate             Solvent %                               Prep.                                                                             (1.0 mole) (1.0 mole)                                                                          Product          (by wt.)                                __________________________________________________________________________    15  K.sup.1  acetate                                                                         Butyl-                                                                              K N-Butylacetamide                                                                             50                                      16  K propionate                                                                             Methyl-                                                                             K N-Methylpropionamide                                                                         55                                      17  K propionate                                                                             Ethyl-                                                                              K N-Ethylpropionamide                                                                          53                                      18  K propionate                                                                             Butyl-                                                                              K N-Butylpropionamide                                                                          48                                      19  K propionate                                                                             t-Butyl                                                                             K N-t-Butylpropionamide                                                                        48                                      20  K propionate                                                                             Hexyl K N-Hexylpropionamide                                                                          45                                      21  K propionate                                                                             Octyl-                                                                              K N-Octylpropionamide                                                                          40                                      22  K β-phenylpropionate                                                                Butyl-                                                                              K N-Butyl-β-phenylpropionamide                                                            39                                      __________________________________________________________________________     .sup.1 K: Potassium                                                      

EXAMPLE 1

The following shows a comparison of two spray foams made in accordancewith the invention with a similar spray foam in which one of thecomponents of the cocatalysts of the invention is lacking. The foamswere sprayed using a Binks 43P gun equipped with a 2640 tip and a 0.026inch preorifice and two each 0.035 inch impingement orifices. A and Bcomponent pressures of 800-1100 psi were used and the volume ratio was1:1. Spray runs were made on cardboard, plywood, or transite board withgood adhesion in all examples. The A component in all three examples ofTable I was a polymethylene polyphenyl isocyanate containing about 40percent by weight of methylenebis (phenyl isocyanate) which had beentreated with a minor amount of monomeric epoxide in accordance with themethod taught in U.S. Pat. 3,793,362 for reducing acidity. The resultantpolyisocyanate had an isocyanate equivalent of about 135 and a percentacidity of less than 0.1%. The B component consisted of a minor amountof a polyol, a surfactant, a blowing agent, and the catalystcombination. Foams A and B employed a catalyst combination ofdimethylcyclohexylamine, dibutyl tin diacetate and potassiumN-phenyl-2-ethylhexamide, along with potassium 2-ethylhexoate (apreviously known trimerization catalyst). Foam C on the other hand didnot contain the hexamide but a large proportion of potassium2-ethylhexoate salt was employed to obtain cream and initiation times inline with Foams A and B. However, the 5 minute firm time for Foam C isan unacceptably long time for a spray application. Foams A and B hadgood firm times and good flame and heat resistance.

                                      TABLE I                                     __________________________________________________________________________    Foams               A       B       C                                         __________________________________________________________________________    Ingredients:                                                                   Component A:                                                                   Polyisocyanate    135     135     135                                        Component B:                                                                   Tris-β-chloropropyl                                                      phosphate         16.6    16.8    16.7                                        DC-193.sup.1      3.32    3.36    3.33                                        Freon 11-B.sup.2  38.7    39.1    38.4                                        LA-700.sup.3      3.32    3.36                                                Polyester I.sup.4 76.3                                                        Polyester II.sup.5        77.2    76.8                                        Dibutyl tin Diacetate                                                                           0.6     0.6     0.6                                         N,N-Dimethyl Cyclohexylamine                                                                    3.32    3.36    3.33                                        Catalyst I.sup.6  2.21    2.24                                                Catalyst II.sup.7 7.74    7.83    11.1                                      Volume Ratio A/B    1:1     1:1     1:1                                       Wt. Ratio A/B       0.9:1   0.9:1   0.9:1                                     Rise Characteristics:                                                          Cream, sec.        :03     :02     :01                                                                           --02                                       Initiation, sec.   :03     :02     :02                                        Rise 1, sec.       :07     :08     :06                                        Rise 2, sec.       :11     :12     :10                                        Tack Free, sec.    :11     :11                                                Firm, sec.         :80     :90     5:00                                      Density, pcf        2.02    2.08    5 minute firm                                                                 time is unac-                             Friability,.sup.8 % wt. loss                                                                      2.0     2.1     ceptable for                                                                  proper spray                              Oxygen Index.sup.9 (%)                                                                            29.3    28.4    application.                              TGA.sup.10 50% wt. loss (at ° C)                                                           445     465                                               TGA % wt. loss at:                                                             400 ° C     39      34                                                 500° C      58      56                                                 600° C      68      66.5                                               700° C      83      77.5                                              __________________________________________________________________________     .sup.1 DC-193: A silicone surfactant sold by Dow Corning Corp.; see, "Dow     Corning 193 Surfactant", Bulletin: 05-146, February, 1966                     .sup.2 Freon 11-B: Trichlorofluoromethane, product of DuPont Corporation.     .sup.3 LA-700: Union Carbide Polyether for Rigid Foams Average Hydroxyl       Number = 700, see "Chemicals and Plastics Physical Properties," Union         Carbide, p. 22, 1969 Edition.                                                 .sup.4 Polyester I: The polyester obtained by esterifying 1 mole of           chlorendic anhydride with 1.1 moles of diethylene glycol and 2.5 moles of     ethylene oxide.                                                               .sup.5 Polyester II: The polyester obtained by esterifying 1 mole of          chlorendic anhydride with 1.1 moles of diethylene glycol and 2.5 moles of     propylene oxide.                                                              .sup.6 Catalyst I: A solution consisting of 43 percent by weight of           potassium N-phenyl-2-ethylhexamide, 28 percent by weight of ethylene          glycol, and 29 percent by weight of dimethyl formamide.                       .sup.7 Catalyst II: A 50% solution by weight of potassium 2-ethylhexoate      dissolved in ethylene glycol.                                                 .sup.8 Friability as measured by the ASTM C421-61 (Reapproved 1967) test.     .sup.9 Oxygen Index, ASTM D 2863-70 test. Flammability test reporting the     percent oxygen content required to sustain sample combustion.                 .sup.10 Thermal gravimetric analysis was performed on a DuPont Model 900      Thermal Analyzer using the Model 950 Thermogravimetric Module.           

EXAMPLE 2

The examples set forth in Table II show a specific embodiment of theinvention as Foam D compared to Foam E which was prepared using acatalyst combination not in accordance with the invention. Both foamswere sprayed on both transite and cardboard using a Grayco Bulldog Model985-928 with a Grayco 232 finishing tip. The systems were sprayed at avolume ratio of 2:1 with component A and B pumps at 1050-1150 psi. FoamD shows superior compressive strength as well as better flame resistanceas measured by the Oxygen Index and Mine Safety Tests when compared toFoam E. Both D and E contained the same polyisocyanate of low acidity asset forth in Example 1 while Foam D was prepared using the same CatalystI as in Foams A and B of the previous Example.

                  TABLE II                                                        ______________________________________                                        Foams               D         E                                               ______________________________________                                        Ingredients:                                                                   Component A:                                                                   Polyisocyanate    134       134                                               Tris(β-chloroethyl)phosphate                                                                15        15                                               L-5340            1                                                           L-5310                      2                                                Component B:                                                                   Polyester III.sup.1                                                                              30                                                         LA-700             10                                                         Hetrofoam-320.sup.2          30                                               Polyol.sup.3                5                                                 n-butanol         2         5                                                 DC-193            1         1                                                 Freon 11-B        28         31.5                                             Dibutyl tin Diacetate                                                                           0.5       0.5                                               N,N-Dimethyl Cyclohexylamine                                                                    3         3                                                 Catalyst I        5                                                           Potassium Acetate           1                                               Volume Ratio A/B    2:1       2:1                                             Wt. Ratio A/B       1.9:1     1.9:1                                           Rise Characteristics:                                                          Cream, sec.        :01       :02                                              Gel, sec.          :03-:04   :07                                              Rise, sec.         :08-:09   :12                                              Firm, sec.         :10       :15                                             Density, pcf        2.36       2.39                                           Compressive Strength (psi)                                                     ##STR6##           27         24.2                                            ##STR7##           24         17.2                                           Friability % wt. loss                                                                             10        9.4                                             Oxygen Index (%)    29         27.5                                           Mine Safety Burn Through.sup.4                                                                    0.6        0.32                                              (hr./in.)                                                                  ______________________________________                                         Footnotes to TABLE II                                                         .sup.1 Polyester III: The polyester used in this example consisted of 27.     parts of the product of esterifying 1 mole of chlorendic anhydride with       1.1 moles of diethylene glycol and 2.5 moles of propylene oxide, blended      with 2.4 parts of diethylene glycol.                                          .sup.2 Hetrofoam 320: A rigid urethane foam polyester polyol based on         chlorendic acid, hydroxyl number = 320. See, "Hetrofoam 320 and               Polyphenylisocyanates in Fire Retardant Rigid Urethane Foams," Service        Bulletin No. 3013, October 1963.                                              .sup.3 Polyol: A polyol formed by the reaction of 3 moles of ethylene         oxide with trimethylolpropane having an equivalent weight of about 93.        .sup.4 Bureau of Mines, flame penetration test.                          

EXAMPLE 3

Foams F and G of Table III were sprayed at component A and B ratios of1:1 and 2:1, respectively, utilizing the same formulation in both FoamsF and G without any catalyst concentration change within the Bcomponent, only the B component ratio adjustment which resulted in thereactant proportions as shown in Table III. The machine employed was aGusmer Model FF Proportioner and the gun, a Gusmer Model D. At the 1:1spray ratio the A and B component pressures were both 800 psi and bothsides employed Gusmer proportioning pumps No. 450-60. At the 2:1 ratio,A component pressure was 900 psi and the proportioning pump was a No.450-60 and the B component pressure was 700 psi and the pump a No.450-30. Foams F and G had similar rise characteristics. The flame andheat resistance of both foams are very similar while the physicalstrength of Foam G is higher than Foam F which is a reflection of thedensity difference. The same epoxide treated polyisocyanate as used inthe previous examples was employed in the formulation of Foams F and G.

                  TABLE III                                                       ______________________________________                                        Foams               F         G                                               ______________________________________                                        Ingredients:                                                                   Component A:                                                                   Polyisocyanate    135       135                                              Component B:                                                                   Polyester III      70        35                                               Tris(β-chloroethyl)phosphate                                                                26        13                                               DC-193            3         1.5                                               Freon 11-B         38.4      19.2                                             Catalyst I        9         4.5                                               Dibutyl tin Diacetate                                                                           0.6       0.3                                               N,N-Dimethyl Cyclohexylamine                                                                    3         1.5                                             Ratio of NCO:OH     1:0.34     1:0.17                                         Volume Ratio A/B    1:1       2:1                                             Rise Characteristics:                                                          Cream, sec.        :02       :02                                              Initiation, sec.   :02       :02                                              Rise 1, sec.       :04       :04                                              Rise 2, sec.       :09       :12                                              Firm               :28       :17                                             Density, pcf        2.1       3.6                                             Friability, % wt. loss                                                                            2         5.3                                             Compressive Strength (psi)                                                     ##STR8##            15.2      35.4                                            ##STR9##            16.8      45.4                                           Mine Safety Burn Through                                                                           0.75      0.87                                              (hr./in.)                                                                  Oxygen Index (%)     30.8      32.8                                           TGA 50% wt. loss (at ° C)                                                                  515       680                                             TGA % wt. loss at:                                                             400° C      24         14.5                                            500° C       47.5      35                                              600° C       58.5      43                                              700° C      67         52                                             ______________________________________                                    

We claim:
 1. In a process for the preparation of a cellular polymer inwhich the major recurring polymer unit is isocyanurate which processcomprises bringing together in the presence of a blowing agent, apolyisocyanate, a trimerization catalyst, and from about 0.01 to about0.3 equivalent per equivalent of said polyisocyanate of a polyol,wherein the improvement consists essentially of employing as thecatalyst, a combination of the following ingredients:a. from 0.005 to0.04 equivalent per equivalent of said polyisocyanate of a tertiaryamine trimerization catalyst; b. from 0.001 to 0.03 equivalent perequivalent of said polyisocyanate of an amide salt having the formula##STR10## wherein M is an alkali metal, R₁, R₂, R₃ can be the same ordifferent and are selected from the group consisting of H, lower alkyl,aryl, aralkyl, and cycloalkyl, R₄ is selected from the group consistingof lower alkyl and aryl; and c. from 0.0005 to 0.005 equivalent perequivalent of said polyisocyanate of a dibutyl tin di(alkanoate) whereinthe alkanoate residue contains from 2 to 12 carbon atoms, inclusive. 2.The process according to claim 1 wherein said polyisocyanate ispolymethylene polyphenyl isocyanate containing about 30 percent to about85 percent by weight of methylenebis(phenyl isocyanate).
 3. The processaccording to claim 1 wherein said polyisocyanate has an acidity lessthan about 0.10 percent.
 4. The process according to claim 1 wherein thepolyisocyanate has been previously mixed at room temperature with about0.25 equivalent to about 1.0 equivalent of a monomeric epoxide perequivalent of acid present in said polyisocyanate to reduce acidity toless than about 0.10 percent.
 5. The process according to claim 4wherein said epoxide is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.
 6. The process according to claim 1 wherein the tertiaryamine is N,N-dimethylcyclohexylamine.
 7. The process according to claim1 wherein the amide salt is potassium N-phenyl-2-ethylhexamide.
 8. Theprocess according to claim 1 wherein the tin salt is dibutyl tindiacetate.
 9. The process according to claim 1 wherein the amide salt ispresent in the form of a solution containing from about 25 percent toabout 75 percent by weight in a diluent.
 10. In a process for thepreparation of a cellular polymer in which the major recurring polymerunit is isocyanurate which process comprises bringing together in thepresence of a blowing agent, a polyisocyanate, a trimerization catalyst,and from about 0.01 to about 0.3 equivalent per equivalent of saidpolyisocyanate of a polyol, wherein the improvement consists essentiallyof employing as the catalyst, a combination of the followingingredients:a. from 0.005 to 0.04 equivalent per equivalent of saidpolyisocyanate of N,N-dimethylcyclohexylamine; b. from 0.001 to 0.03equivalent per equivalent of said polyisocyanate of potassiumN-phenyl-2-ethylhexamide; and c. from 0.0005 to 0.005 equivalent perequivalent of said polyisocyanate of dibutyl tin diacetate.
 11. Theprocess according to claim 10 wherein the polyisocyanate ispolymethylene polyphenyl isocyanate containing from about 30 percent toabout 85 percent by weight of methylenebis(phenyl isocyanate).
 12. Theprocess according to claim 11 wherein said polyisocyanate has an acidityless than about 0.10 percent.
 13. The process according to claim 11wherein said polyisocyanate has been previously mixed at roomtemperature with about 0.25 equivalent to about 1.0 equivalent of amonomeric epoxide per equivalent of acid present in said polyisocyanateto reduce acidity to less than about 0.10 percent.
 14. The processaccording to claim 13 wherein said epoxide is3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate.
 15. Theprocess according to claim 10 wherein said amide salt is present in theform of a solution from about 25 percent to about 75 percent by weightin a diluent.
 16. The process according to claim 15 wherein said diluentis a mixture of ethylene glycol and dimethyl formamide.